SFB Successfully Held Winter School 2023 in Hirschegg, Kleinwalsertal

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After being postponed due to the pandemic situation, SFB 1083’s Winter School 2023 took place in presence from February 27th to March 3rd, 2023 at Marburger Haus in Hirschegg, Kleinwalsertal, Austria.

Groupfoto of the 40 participants. (Foto: Maximilian Dreher)

The 40 participants came from four collaborating institutions (33 from Philipps-Universität Marburg, four from Justus-Liebig-Universität Gießen, two from Universität Leipzig and one from Forschungszentrum Jülich). The event was organized by the SFB student speaker including 29 PhD Students, seven Master students and four postdoctoral researchers.

After a joint bus-ride from Marburg the program started with an official welcome and a first program overview by Maximilian Dreher, organizer and SFB student speaker. During the subsequent dinner, the participants started some first scientific discussions across departmental boundaries.

Poster session during the winter school. (Foto: Maximilian Dreher)

17 talks distributed over six sessions at three days were chaired by postdocs and experienced PhD students. The idea was to give introductory talks, such that everyone regardless of the own discipline and scientific experience could follow the topic to broaden the own horizon. Therefore, the talks were given an extra 10 min of discussion to answer as many open question as possible. All presenters did an excellent job of sharing their experience with the audience.

Highlights were talks by Carolin Kalff and Dominik Scharf, who presented a detailed lab day of an organic chemist or the talk by Willy Knorr, who gave insights into how to simulate transport characteristics of excitons.

Two poster session were held in the evenings after the dinner. Since only 12 poster per session were presented, everyone got the opportunity to have deep discussions at every poster. The overall atmosphere was very stimulating, such that the end of both sessions was late in the evening with many people still in discussion.

Besides the scientific program, the students got the opportunity to explore the beautiful landscape of Kleinwalsertal and enjoy the fresh air, while discussing the new insights they got during the week.

Chemical Doping by Fluorination and Its Impact on All Energy Levels of π-Conjugated Systems – Publication by A2 (Witte) and A8 (Koert/Dürr)

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In their combined experimental and theoretical study published in the Journal of Physical Chemistry Letters, the groups of Holger Bettinger (Uni Tübingen), Ulrich Koert (A8) and Gregor Witte (A2) investigated the impact of fluorination on the C1s core level energies in fluorinated acene derivates.

Fluorination affects the inner potential and thus the energy levels, as symbolized by the water level. The electron binding energies are probed via X-ray photoelectron spectroscopy (XPS). (Image: Y. Radiev, Reprinted with permission from ACS J. Phys. Chem. Lett. 2023. Copyright 2023 American Chemical Society.).

Fluorination is commonly used to tailor the frontier energy levels. In the present study, the authors utilized the recent achievements in the synthesis of regio-selectively fluorinated acenes and systematically investigated the core level binding energies by means of X-ray photoelectron spectroscopy (XPS) complemented by density functional theory (DFT) calculations.

These investigations reveal that fluorination leads to core level shifts, which are not limited to directly fluorinated carbon atoms, but also affect more distant carbon atoms. These shifts depend on the degree of fluorination, indicating that local fluorination affects the electron density of the entire aromatic system similar to doping. Since commonly core level shifts are used as fingerprint signatures for the identification of molecular entities, the new results challenge this method for fluorinated π-conjugated molecules. Moreover, as these shifts do not only influence the core levels, but also the molecular valence orbital energies, transitions from the former into the latter are hardly affected by fluorination, as verified by X-ray absorption spectroscopy (NEXAFS) measurements.

Overall, the results show that not only the energies of frontier orbitals but also of all core levels in fully π-conjugated systems are affected by local fluorination, hence limiting a chemical identification based on supposedly characteristic core level energies since they instead depend also on the degree of fluorination.

Publication

D. Bischof, Y. Radiev, M.W. Tripp, P.E. Hofmann, T. Geiger, H.F. Bettinger, U. Koert, G. Witte
Chemical Doping by Fluorination and Its Impact on All Energy Levels of π-Conjugated Systems
J. Phys. Chem. Lett. (2023) DOI:10.1021/acs.jpclett.3c00287

Contact

Prof. Dr. Gregor Witte
Philipps-Universität Marburg
SFB 1083 project A2
Tel.: 06421 28-21384
EMAIL

Poster Presentation Prize at DPT 2022 in Karlsruhe

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Marleen Axt (B6) was awarded for the best poster presentation at the 26th German Conference of Women in Physics („Deutsche Physikerinnentagung“, DPT) in Karlsruhe

Poster: „Time-resolved second-harmonic imaging microscopy: Ultrafast processes in ultrathin materials“ by M. Axt, J. E. Zimmermann, G. Mette, and U. Höfer (Philipps-Universität Marburg).

The German Conference of Women in Physics takes place annually since 1997. Supported by the German Physical Society (DPG), it offers female scientists of all areas of physics and at different carrier levels – from student to professor as well as physicists in industry – the possibility for networking and professional exchange. The 2022 conference had 250 participants and was hosted by the Karlsruhe Institute of Technology (KIT) from November 24-27, 2022.

In her contribution, Marleen Axt (project B6) reported on investigations of ultrafast charge-transfer processes between van-der-Waals monolayers of different twist angles by means of time-resolved second-harmonic imaging microsocopy, a technique developed by the Höfer group. The experiments provide insight into fundamental electronic properties at interfaces.